The purpose of this project is to study the long-term health effects of therapeutic drugs as they may relate to carcinogenicity. Cohort studies of exposed groups are conducted, as well as case-control studies of selected cancer sites which involve lifetime drug use histories. Emphasis has been on the evaluation of various hormonal preparations, immunosuppressive drugs, and cancer chemotherapeutic agents. No general effects of thyroid medications or tranquilizers have been seen on breast cancer risk, but menopausal estrogens seem to increase the risk of benign breast disease. Oral contraceptives did not influence the risk of endometrial or ovarian cancers, but did seem to exert a protective effect on fibrocystic disease of all histologic subtypes. Alkylating agents used for treatment of cancer and some non-neoplastic conditions were found to be associated with large excess risks of leukemia that were apparently dose related. Future analyses are planned to evaluate the effects of estrogenic preparations on a variety of female tumors and to assess, systematically, the role of adjuvant drug therapy among patients treated for a number of different cancers.